During his defense when on trial for his life, Socrates, according to Plato's writings, pointed out that dissent, like the gadfly, was easy to swat, but the cost to society of silencing individuals who were irritating could be very high. "If you kill a man like me, you will injure yourselves more than you will injure me," because his role was that of a gadfly, "to sting people and whip them into a fury, all in the service of truth." This may have been one of the earliest descriptions of gadfly ethics.

In modern politics, a gadfly is someone who persistently challenges people in positions of power, the status quo or a popular position.[3] For example, Morris Kline wrote "There is a function for the gadfly who poses questions that many specialists would like to overlook. Polemics are healthy."[4] The word may be uttered in a pejorative sense, while at the same time be accepted as a description of honourable work or civic duty.[5]

The Book of Jeremiah uses a similar analogy as a political metaphor. "Egypt is a very fair heifer; the gad-fly cometh, it cometh from the north." (46:20, Darby Bible)